1. Field of the Invention
The invention relates to a vehicle control apparatus for a vehicle employing a brake override system (BOS) that reduces an engine output in response to simultaneous operations of an accelerator and a brake.
2. Description of Related Art
A BOS such as that described in Japanese Patent Application Publication No. 2010-038051 (JP 2010-038051 A), for example, is available as a control mechanism employed in a vehicle. A BOS is a control mechanism that prioritizes a brake function when an accelerator and a brake are operated simultaneously. In response to simultaneous operations of the accelerator and the brake, the BOS reduces an engine output, and as a result, a braking force generated by the brake exceeds a driving force generated by an engine.
A Traction Control (TRC) system, meanwhile, is available as a control mechanism that performs engine output control independently of an accelerator operation amount. A TRC system reduces the engine output when traction is lost in vehicle wheels in order to prevent tire slip during startup and acceleration.
In a vehicle employing both the BOS and the TRC system described above, the BOS may be activated in response to simultaneous operations of the accelerator and the brake in a condition where the engine output has been suppressed by the TRC system. FIG. 6 shows a condition occurring at this time. In FIG. 6, a BOS required value is a required value of a control accelerator operation amount required by the BOS, and a TRC required value is a required value of an accelerator operation amount value required by the TRC system. A smallest value among an actual accelerator operation amount, the BOS required value, and the TRC required value is set as the control accelerator operation amount used to calculate a throttle opening required value.
In FIG. 6, the brake is operated at a time T1 during travel in a condition where the engine output is suppressed by the TRC system, and as a result, the BOS is activated. When the BOS is activated, the BOS required value is reduced gradually from the actual accelerator operation amount. When the brake is operated, on the other hand, the traction of the vehicle wheels improves, and therefore the TRC required value increases gradually from the time T1. In FIG. 6, the TRC required value is lower than the BOS required value from the time T1 to a time T2, and therefore the control accelerator operation amount used to determine the throttle opening temporarily increases immediately after the time T1 at which the brake is operated.
Hence, in a vehicle employing both a BOS and a TRC system, the engine output may increase temporarily even though the BOS is operative. In this case, the engine output increases even though a driver assumes that the engine output is being suppressed by the BOS, and as a result, the driver may have a feeling of strangeness.
Note that when a control mechanism other than a TRC system which also performs engine output control independently of the accelerator operation amount is employed, the engine output may likewise increase temporarily, while the BOS is operative, in response to a request from the control mechanism.